Heater



FIG. 1 is a front elevation view of the heater;

FIG. 2 is a back elevation view of the heater;

FIG. 3 is a right elevation view of the heater;

FIG. 4 is a left elevation view of the heater;

FIG. 5 is a top elevation view of the heater; and,

FIG. 6 is a top perspective view of the heater.

The broken line portions of the drawings depict environmental structure that forms no part of the claimed design. 

The ornamental design for a heater, as shown and described. 